Submerged Turbines Could Replace 10 Nuclear Reactors In Japan

Okinawa Institute of Science and Technology (OIST) researchers have developed turbines to convert the power of ocean waves into clean, renewable energy.

Professor Shintake and the Quantum Wave Microscopy Unit at OIST began by starting a project titled “Sea Horse,” aiming to harness energy from the Kuroshio ocean current that flows from the eastern coast of Taiwan and around the southern parts of Japan.

That project used submerged turbines anchored to the sea floor through mooring cables that convert the kinetic energy of sustained natural currents in the Kuroshio into usable electricity, which is then delivered by cables to the land. The initial phase of the project was successful, and the Unit is now searching for industry partners to continue into the next phase. But the OIST researchers also desired an ocean energy source that was cheaper and easier to maintain.

This is where the vigor of the ocean’s waves at the shoreline comes into play.

The blades of this five-blade turbine are made of a soft material and they rotate on their axis when influenced by ocean waves – the diameter of the turbine is about 0.7 meters. The axis is attached to a permanent magnet electric generator, which is the part of the turbine that transforms the ocean wave energy into usable electricity. The ceramic mechanical seal protects the electrical components inside of the body from any saltwater leakage. This design allows the turbine to function for ten years before it need replacing. Image Credit: Okinawa Institute of Science and Technology Graduate University, Quantum Wave Microscopy Unit. Click image for the largest view.

Shintake explained, “Particularly in Japan, if you go around the beach you’ll find many tetrapods,” Tetrapods are concrete structures shaped somewhat like pyramids that are often placed along a coastline to weaken the force of incoming waves and protect the shore from erosion. Similarly, wave breakers are walls built in front of beaches for the same purpose. “Surprisingly, 30 percent of the seashore in mainland Japan is covered with tetrapods and wave breakers,” he said. Replacing these with “intelligent” tetrapods and wave breakers, Shintake explained, with turbines attached to or near them, would both generate energy as well as help to protect the coasts.

Professor Shintake pointed out, “Using just 1 percent of the seashore of mainland Japan can [generate] about 10 gigawats [of energy], which is equivalent to 10 nuclear power plants. That’s huge.”

In order to tackle this idea, the OIST researchers launched The Wave Energy Converter (WEC) project in 2013. WEC involves placing turbines at key locations near the shoreline, such as nearby tetrapods or among coral reefs, to generate energy. Each location allows the turbines to be exposed to ideal wave conditions that allow them not only to generate clean and renewable energy, but also to help protect the coasts from erosion while being affordable for those with limited funding and infrastructure.

The turbines themselves are built to withstand the forces thrust upon them during harsh wave conditions as well as extreme weather, such as a typhoon. The blade design and materials are inspired by dolphin fins – they are flexible, and thus able to release stress rather than remain rigid and risk breakage.